Magnetic field sensors for sensing a magnetic field in low power applications are known. One such device is sold by Allegro Microsystems, Inc. of Worcester, Mass., the assignee of the subject invention, under part no. A3211. This device includes a Hall effect element for sensing the presence of a magnetic field of predetermined strength in a pole insensitive manner (i.e., regardless of the orientation of the magnetic article relative to the Hall effect element). The device includes a low power feature whereby portions of the device are activated for only a short. “awake” time interval during each clock cycle. Suitable low power applications include battery-operated, hand-held equipment, such as cellular and cordless telephones, pagers, palmtop or handheld computers, personal digital assistants (PDAs), and the like.
Magnetic field sensors for sensing rotational direction and speed of a rotating magnetic article, such as a rotating ring magnet, are also known. One such device is sold by Allegro Microsystems, Inc. of Worcester, Mass., the assignee of the subject invention, under part no. 3422. In particular, this device includes two Hall effect elements on the same silicon substrate and processing circuitry for providing a speed output signal indicative of the speed of rotation of the magnet and a direction output signal indicative of the direction of rotation of the magnet.